This game was bought 4 years ago, when it came out, and is still one of the biggest disappointments to come out on ps3. The game is utterly repetitive and requires you to kill a marked person in every level and, whilst this seems engaging, the nature of the game simply just revolves around killing a person and then moving on to the next target.
The repetitive nature of the game hinders it but it still is engaging to traverse the city. The city is amazingly detailed and full of wonderful things to see (especially considering the graphics are simply stunning). However, there is very little to do in the game as a whole and this takes detracts from the experience.
Additionally, the worst feature of the game is that the whole city isn't open for you to explore unless you climb a marked building in a few areas of the game in order to open up the city. This is frustrating because the game doesn't do a good job of guiding you or telling you which exact buildings you need to climb to complete the task.
Overall, whilst the game has decent gameplay (I love the wonderful climbing mechanics) it is hindered by a few odd design choices (climbing stupid towers ehhmmmm....) and a lack of tasks to do. If you want a similar but better experience, play Assassins Creed 2 and Brotherhood which are far superior games (especially the 2nd game).